1. Field of the Invention
The present invention relates to optical communication equipment and, more specifically but not exclusively, to wavelength-division-multiplexing (WDM) transceivers.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Wavelength-division-multiplexing (WDM) technology uses multiple carrier wavelengths to transmit multiple communication signals over a single optical fiber. The carrier wavelengths usually correspond to a rigid wavelength grid, such as a 50-GHz or 100-GHz International Telecommunication Union (ITU) grid. A representative WDM system uses an optical multiplexer at the transmitter to join modulated optical carriers together for transmission over an optical fiber, and a de-multiplexer at the receiver to split the received modulated optical carriers apart for detection. An arrayed waveguide grating (AWG) is often used to implement the multiplexer at the transmitter and/or the de-multiplexer at the receiver.
One problem with AWGs is that their spectral characteristics are very sensitive to manufacturing-process variances, such as variances in the refractive indices of the constituent waveguides. As a result, special technical solutions are needed to attain an acceptably high manufacturing yield of AWGs for use in a WDM receiver/transmitter. However, many solutions are either incompatible with production-line manufacturing or not sufficiently cost effective.